Michael Werner, Astrophysicist and Space Science Leader

Infrared astronomy uses infrared radiation to observe and analyze objects in space. Infrared wavelengths are invisible to the unaided human eye, so it is something of an astronomical wonder that many of the most spectacular images and discoveries relating to the formation and evolution of stars, the composition of the interstellar medium, the detection of exoplanets, and even the large scale structure of the universe were all made possible using infrared astronomy. In the discussion below, Michael Werner reflects on his five decade-long career in infrared astronomy, and his service as Project Scientist of the Spitzer Space Telescope, one of the most successful and long-lasting space telescopes in history.

Werner developed his interests in astronomy as an undergraduate at Haverford College, and his time as a graduate student at Cornell University coincided with fantastic technological advances that pushed infrared astronomy into the modern era. After formative postdoctoral experiences, first at the University of Cambridge and then UC Berkeley, Werner joined the faculty at Caltech, where Gerry Neugebauer and others were leading the way to make campus and JPL a dual powerhouse in infrared astronomy. Werner's perspective below offers inspiration and life lessons: he did not achieve tenure at Caltech, but rather than become embittered and alienated, he explains why this was the best career move that ever happened to him. This can be understood partly as the importance of seeking new opportunity after a setback, and partly because the professor's life is not necessarily the right fit for everyone.

After leaving Caltech, Werner joined the astrophysics group at NASA Ames to work on the Kuiper Airborne Observatory, and where the early studies that would eventually meld into the Spitzer Space Telescope were underway. At the invitation of Charles Elachi, who would go on to become JPL Director, Werner came back to JPL where he was named Project Scientist for Spitzer, which launched in 2003, twenty years after his appointment. His explanation of the development of the telescope, and its relation to the broader mission of NASA and JPL's entree into astrophysics are a definitive account of this important milestone in space history, as are his explanations of the many "firsts" that Spitzer achieved including, most dramatically, the first light detected from an exoplanet, thereby launching the world of exoplanet research.

Today, the astronomy community is rightly transfixed by the technological prowess of the James Webb Telescope, and its findings are already revolutionizing our understanding of the universe. As Werner explains - and what is always true in science - today's successes are built on yesterday's innovations. It would be too simplified to say that Spitzer begot Webb, but it is undeniable that Webb's achievements were made possible in large part by Spitzer. Perhaps an even greater legacy is that the Spitzer Telescope is not even an artifact of history: while the mission is over, the enormity and significance of the data it collected remains an intense focus of research. And for Werner, who like so many great scientists has found it hard to retire, the current focus is on SHEREx, another Caltech-JPL collaboration, which will test the theory of cosmic inflation, and which will get us ever closer to understanding the origins of the universe.

ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It's Monday, September 11th, 2023. I'm delighted to be here with Dr. Michael Werner. Michael, it's wonderful to be with you. Thank you for joining me today.

MICHAEL WERNER: Glad to be here, David.

ZIERLER: Michael, to start, would you tell me please your title and institutional affiliation.

WERNER: I'm a largely but not totally retired Senior Research Scientist at JPL. I am also the Project Scientist for the Spitzer Space Telescope, which was one of NASA's Great Observatories. Spitzer was retired in January of 2020, but I maintain the title. I'm also a JPL Fellow. In addition, I'm a visiting Associate at Caltech. What I'm primarily doing now is using my expertise in support of physics and astronomy missions and people at JPL. I manage JPL's use of the Palomar Observatory. We have a 25% share. I'm a Co-investigator in a new exciting MIDEX mission called SPHEREx, which is led by Jamie Bock here on campus.

ZIERLER: Michael, have you failed at retirement, or is this sort of the plan that you're sort of steadily decreasing responsibilities? Because it sounds like you have a lot going on right now.

WERNER: Yeah. I probably made it sound a little more grandiose than it is. But I'm saying I'm gradually slacking off from major responsibilities.

ZIERLER: Now, the designation research fellow at JPL, I know that's an honorific. Is that sort of like an emeritus designation in academic institutions?

WERNER: No, it's a JPL fellow. That's a designation. It's to recognize and reward outstanding JPL scientific, technical, and business staff, not managers but people who actually do the work. It's an honorary position. The supposition is that this would be a font of expertise that could support JPL activities in the future, but that never seems to have happened. It's an obvious thing to have people at this level be mentoring younger people across the laboratory. But nothing like that has ever been organized systematically.

SPHEREx Testing of Cosmic Inflation

ZIERLER: Michael, let's start with the most recent first. Tell me about your work on SPHEREx, and your partnership with Jamie Bock, and what the objectives of the mission are.

WERNER: SPHEREx is a very exciting astrophysics MIDEX to be launched in January of 2025. It gets spectra over the entire sky. A spectrum is a measurement of the composition or motion or physical conditions in a source beyond just taking a picture. These spectra will be obtained with quite precise spatial resolution of six arcseconds, and the spectral resolution, the divisions of the spectrum between 42 and 130, the so-called resolving power. I helped Jamie with the proposal and the concept development. Of course, he was way ahead of me. It is a very clever mission. We could go into that if you like. My main role is, again, as a kind of senior overseer, who can say "Based on my Spitzer experience, maybe we should do this." Also, I'm a member of the team which is doing one of the three SPHEREx science themes. There's a cosmic inflation theme, a Galaxy formation theme, and an interstellar/circumstellar/planetary ices theme. These all get their data at different points in the orbit. It's very cleverly designed. At the pole of the orbit, it's a polar orbiter going around the Earth's poles, from south to north pole. At the pole, which we cross repeatedly, is where we're doing the Galaxy formation theme. The cosmic inflation theme is over much of the sky looking at distant galaxies. The ices theme is in the plane of the Galaxy where it's not possible to look in the deep space, but we can see interstellar and circumstellar ices in stars and through molecular clouds and the like. I am working on the ices team, which is headed by Gary Melnick from Harvard.

ZIERLER: Now, when you say cosmic inflation is the goal to see if the theory is true—?

WERNER: Their goal is to see whether how—one of the implications for the details of inflation of the distribution of galaxies in space has to do with something called non-Gaussianity. Are the distances between galaxies distributed according to Gaussian curves, so to speak, or the deviations from that? That contains information about the character of inflation.

ZIERLER: I'll ask a very pointed question. If this does what you're aiming for it to do, is the verification of a type that Alan Guth might finally get a Nobel Prize?

WERNER: I don't think so, but it would presumably—this is not my field—but it would presumably, depending on what we come up with, rule out many theories of the details of inflation.

ZIERLER: Because there's many theories of inflation?

WERNER: Yeah, exactly.

ZIERLER: I want to ask about the afterlife of Spitzer. Is there still data to be pored through? Are we still learning things from the mission?

WERNER: Absolutely. Getting back to your theme of astronomical data and data science, one of the things that enables that is that all NASA missions, certainly on the scale of Spitzer, or even SPHEREx, now place their data in a readily accessible public archive. At the end of the mission, one goes through the data, reduces it with common software tools, which have been developed over the mission, and then it's stored in a readily accessible way. People can access this archive and use it either by itself or in conjunction with data from other missions, in order to advance our astrophysical understanding. Most notably, since JWST, which although you wouldn't necessarily know it from the publicity, is as much a successor to Spitzer as it is to Hubble, many of the JWST publications which impinge upon the Spitzer wavelength range cite, Spitzer data, one way or another. The data are definitely still alive, even though the mission is no longer adding to the archive.

ZIERLER: Are there staff who are exclusively attached to the Spitzer mission, or how long of an administrative afterlife is there?

WERNER: There's a wonderful facility here at campus called IRSA, which is the Infrared Science Archive, and Spitzer has now been swept up and included in the IRSA archive. The IRSA archive is well staffed. Now, I don't know the details. I imagine that at the present time, they have several people on their staff who are real experts with Spitzer; in time that the cutting edge may transfer to other archival datasets. But there'll always be somebody there to help people find their way to the Spitzer data.

Infrared Astronomy 101

ZIERLER: Let's go really broad now with your area of expertise. Is it infrared astronomy? Is that your basic home base academic discipline?

WERNER: Yes.

ZIERLER: Let's do some infrared astronomy 101. What does that mean? What is the infrared in an astronomical context?

WERNER: The infrared is, in terms of the electromagnetic spectrum and wavelength and the like, it's sort of longward of what we can see with our eye extending out into microwaves. We now know, of course, that the entire electromagnetic spectrum, starting with gamma rays and going off to radio, is necessary to get a complete understanding of astrophysical phenomena. In many cases, a particular object might be studied all across the spectrum, but each piece of the spectrum has some unique attributes that it brings to the picture. In the case of the infrared, we summarize them as the old, the cold, and the dirty, which as I like to say is not the title of an unreleased Clint Eastwood movie.

ZIERLER: [laugh]

WERNER: But it highlights three things that are fairly unique to the infrared. When we talk about "the old", we're referring to the fact that the universe is expanding, and more distant objects are moving away more rapidly. They do that because space is being stretched. As it's stretched, the wavelength of radiation that these objects emitted is being stretched as well. Consider a distant Galaxy that radiates in the optical and the ultraviolet. That light comes to us in the infrared because of this phenomenon which we call the cosmic redshift. The radiation is stretched, and its wavelength increases toward the red. Red light has a longer wavelength than blue light, and infrared light has a much longer wavelength. In the infrared, we see there many objects which are so distant that their optical, and ultraviolet radiation shifts entirely into the infrared, and they can't really be seen at the shorter wavelengths. The infrared is thus very important for studying, the most distant, oldest objects we can see. "The cold" alludes to the fact that all objects in space, anywhere, radiate electromagnetic radiation in a way which is related to their temperature. The hotter they are, the shorter the wavelength, the more the radiation comes out in the visible or in the ultraviolet. The sun is at a temperature of 6,000 degrees Kelvin or 10,000 degrees Fahrenheit that temperature produces visible light radiation as a result of the basic laws of physics. For a much colder object, like the planet Jupiter, which is at a temperature of 80 degrees or something like that, its intrinsic radiation comes out in the infrared because it's at a lower temperature corresponding to a longer wavelength of light. Now you see Jupiter in visible light because it reflects the sunlight. But, in fact, the radiation that Jupiter itself produces comes out in the infrared. We cite "the cold" because objects like the coldest stars and material around and between the stars, and even exoplanets [planets around other stars], radiate the bulk of their intrinsic radiation, which has a lot of information about their characteristics, in the infrared part of the spectrum. It is sometimes useful to think of infrared radiation as heat radiation, as demonstrated by the infrared lamp one might have in the bathroom. "The dirty" relates to the fact that there is a substance called cosmic dust, which is about 1% of the matter in space between the stars.

This cosmic dust is very effective at absorbing visible and ultraviolet light, say, from a nearby star or a forming star that's swathed in this cosmic dust, and heats the dust up to a temperature where it radiates in the infrared. I like to say that cosmic dust is an infrared astronomer's best friend. If you look at the radiation in space, there's about as much radiation due to stars in the visible and the UV as there is in the infrared. This is due to the fact that cosmic dust absorbs about half of the starlight and re-radiates it in the infrared. A Galaxy like our own Milky Way which is not at all unusual, has got a lot of dust in it. You see it in various coffee table photographs. That dust is actively producing infrared radiation. The other thing about the dust is that a cloud of it is more transparent in the infrared than in the visible. That's again the result of the laws of physics, and the size of the particles. Regions of our Galaxy, like the center of our Galaxy, which are hidden from us by the dust along the line of sight in the plane of the Galaxy, that dust is largely transparent in the infrared. One of the early triumphs of infrared astronomy was the detection of the Center of the Galaxy where we now know, largely through infrared observations, that there's a dense stellar cluster and a giant black hole.

ZIERLER: Now, is infrared astronomy equally relevant for land-based and space-based telescopes?

WERNER: That's a very good question. If you observe from the ground in the infrared, well, there are two challenges. One is that the atmosphere, even at a best mountaintop site like Maunakea, is opaque over large sections of the infrared.

ZIERLER: Even with adaptive optics?

WERNER: Adaptive optics doesn't help because the light's not getting through the atmosphere.

ZIERLER: Right. [laugh]

WERNER: When you observe those absorbed wavelengths, to get a complete picture in the infrared, you need to go into space. More fundamentally, if you're observing on the ground from a warm telescope looking through the warm atmosphere, the infrared radiation from that foreground material comes into your telescope, and will obliterate or not cancel but overwhelm the fainter radiation from a distant celestial source. If you want to do the most sensitive possible observations, you want to go into space so you can cool your telescope. Then that just opens up the infrared sky in an unprecedented fashion.

ZIERLER: You mean literally cool down the telescope?

WERNER: Cool down—

ZIERLER: The detector?

WERNER: Yeah, the whole kit and caboodle, down to very low temperatures, including temperatures as low as a few degrees above absolute zero, perhaps even colder. Now, before we go there, getting back to your question, with a big telescope, say a 30-meter telescope, and adaptive optics, which allows you to focus in precisely on the target you're looking at, and eliminate a lot of the nearby empty sky, you can certainly observe with high sensitivity, particularly if you're interested in spectroscopy, where you're dividing the light up, and this cosmic background is less of a problem. For high spatial resolution imaging and high-resolution spectroscopy at selected infrared wavelengths, the ground probably will have an edge over space because the telescopes can be bigger. But for lower resolution spectroscopy, photometry, imaging, and surveying large regions of the sky, you can't beat a cryogenic telescope in space, which is why Spitzer and now the James Webb Space Telescope have been so path breaking. However, I should emphasize that the first generation of modern infrared astronomers struggled successfully against the limitations discussed above and produced very important and exciting results from telescopes on the ground. These of course ultimately paved the way for space observatories such as Spitzer and JWST.

ZIERLER: Now, the JWST, is it that it has infrared capabilities, or it's more proper to think of it as an infrared telescope?

WERNER: The James Webb runs in wavelength from the extreme visible above .6 microns towards the long wavelength end of the sensitivity of the human eye - out into the thermal infrared, where you're really seeing emissions from cooler objects at about 25 microns. It bridges the gap between Hubble, which works out to about maybe 2 microns at the longest, and Spitzer, which started working at 3.6 microns. It's a telescope which is capable of both visible light and infrared investigations. Technically, most of its wavelength region is in the infrared because it's beyond what your eye can see. On the other hand, in terms of a detector technology, it's a little more of a hybrid because it uses, I believe, it uses detector arrays which are sensitive from .6 microns out further into the infrared. The telescope is cooled to enhance its infrared sensitivity, and the arrays which detect the radiation are cooled further yet.

The Search for Life Beyond Earth

ZIERLER: Michael, the great question of our time, perhaps in all of humanity's time, are we alone in the universe, we can now refine that question to focus specifically on biosignatures and technosignatures and exoplanets.

WERNER: Exactly.

ZIERLER: How will infrared telescope technology help get us closer to answering that question? What can it do in this application better than other forms of astronomical observation?

WERNER: There are a number of important—starting with Spitzer, exoplanets were discovered in 1995 or 1996 when the Spitzer development was well along. But Spitzer was such a well-designed and—what do I want to say?—consistent and reliable, stable platform that it was able to do very precise measurements related to exoplanets. Spitzer was the first instrument to detect the intrinsic [infrared] radiation from an exoplanet. Spitzer also shows that it is possible to study the atmosphere of an exoplanet in the infrared by looking at the starlight that filters through it.

This has to do with exoplanets – planets around stars other than the sun, Spitzer studies "transiting" exoplanets that, as seen from Earth, move in front of and behind the star that they're orbiting, which was a great discovery of the Kepler mission, of course. The exoplanet cannot be seen separately from its host star. But Spitzer showed that when the planet goes behind the star, you no longer see the infrared light from the planet, so that the total infrared radiation seen by Spitzer [or even better by JWST] drops. That infrared light returns as the planet comes out from behind the star. It will contain the imprint of the molecules that were in the atmosphere of the planet, if it has an atmosphere. Then when the planet moves in front of the star, you can see the starlight—now, this can be done in the visible as well as the infrared—filtering through the atmosphere of the planet, again, if it has one, and study the composition of the atmosphere. [In addition, the total light from the system drops because the planet is now blocking the star, so one can determine the size of the planet relative to the size of the star, or the size of the planet as the size of the star is often well-known.] In the infrared, you have access to molecules like water, methane, carbon dioxide, carbon monoxide, which are of great interest for biogenic processes. Now, that's definitely setting the stage for studying habitability, and identifying potentially habitable planets, and so forth. The way things are going now, the best technique—I believe this is correct—for actually studying the composition of an exoplanet is to use an instrument called a coronagraph, which blocks out the light from the star, and that's more easily done. That's very hard to do but more easily done in the visible than in the infrared.

ZIERLER: Why is that?

WERNER: Basically, it's because of diffraction. If you're working at .5 microns as opposed to 5 microns, your intrinsic image size is 10 times smaller, so you can creep in that much closer to the star. Your coronagraph blotting out the light from the star will allow you to look much closer into the star because the star image is smaller than in the infrared. The planet doesn't care. The planet's where the planet is. That's a good part of the reason. To be complete, I should mention that another possibility for studying exoplanets in detail, again more credible in the visible than in the infrared, is to use what is called a starshade, which has to be some [very large' distance from the exoplanet and its host star.

ZIERLER: Michael, another big mystery, of course, dark energy and dark matter. What role do you see infrared astronomy playing and helping us understand what these things are?

WERNER: One of the major, I think, with regard—yeah, I think this is right. There's a recently launched ESA-NASA mission called Euclid, which will be working in the very near infrared around 1-to-2 micron or so, doing precise imaging of the sky around clusters of galaxies to see the evidence of a gravitational lensing that these galaxies produce on galaxies behind them. The galaxies behind them, as their light passes a foreground Galaxy or a foreground cluster of galaxies, it is distorted due to the gravity by a process called gravitational lensing, by the gravity of the mass. One doesn't know for sure what the mass is, because much or most of the mass of a Galaxy or a cluster of galaxies is in the form of dark matter. Euclid will help figure that out. In addition, by studying this lensing phenomenon at galaxies at a range of distances, you can find out something about dark energy because of the way that it affects the expansion of the universe. There was a quantity called the dark energy equation—oh, wait a second; I think this is right—the dark energy equation of state which one can constrain with a mission like Euclid or a follow-on mission that JPL has a big role in called the Roman Space Telescope, to be launched later in the decade. In terms of determining, so there are lots of things that can be done in the infrared to look at the effects of dark matter or dark energy. Whether that gets down to the fundamental characterization of the particles responsible or the processes responsible is a different question.

ZIERLER: Sure. What about the role that infrared astronomy plays in concert with other forms of astronomy? Where is it an enabler? Where does it, you know, for radio astronomy or optical astronomy, in the symphony of just the astronomical discipline, what does infrared add at that broad level?

WERNER: I think to answer, well, I think its most salient contribution is in this ability to look back in space and time, and see objects which aren't readily seen at shorter wavelengths anymore because they're too highly redshifted that down away that that's a playground that only the infrared plays in by definition this way, but it's so fundamental that people of course are extremely interested in it. When you hear that there's concern because there are too many massive galaxies at very high redshifts, that's undoubtedly based largely on infrared observations. I think in the study of exoplanets, that's of great interest across the electromagnetic spectrum and its infrared as its unique contributions to make, as we discussed earlier. Star formation is a fundamental issue that's of interest to all astronomers, stellar and planetary system formation, and a lot of that study is best done in the infrared because as a star forms, it tends to be cold, and it tends to be shrouded in dust. My earlier discussion in the case of that plays right into the cold and dirty sub-themes of infrared, and so infrared observations are essential for the study of star formation and planetary system formation which again are essential ingredients of our understanding of astrophysics.

If you look at things like the history of cosmic star formation or the buildup of cosmic mass at shorter wavelengths, that's informed by optical/ultraviolet radiation observations. But as you move into more distant space, you pick up on it with the infrared, and that us another fundamental problem that is best addressed in the infrared. In addition to that, there are lots of investigations which are only complete when you include the infrared, for example, the characteristics of galaxies powered by black holes and the black hole mass and those kinds of things. Again, much of that information is in the infrared because the whole process may be shrouded in dust, although in that case you might be able to see it as well with X-rays or with radio waves. However, it is important to remember that much of modern astrophysics research relies on data from across much or most of the electromagnetic spectrum.

ZIERLER: Michael, what about the quest to get as close as possible to the singularity, the Big Bang, T equals zero? What can infrared astronomy do that other forms cannot?

WERNER: I think what the infrared can uniquely do is to trace the formation of galaxies, condensed objects, and so on forth back as far in the space and time as they can be seen, and perhaps help understand how the earliest galaxies formed.

ZIERLER: This is a surprise now, according to what JWST is showing us.

WERNER: Exactly. As I said, that's largely based on infrared studies. At some point, the objects are going to be too distant and too faint, and you have to rely on microwaves to study the cosmic microwave background, which is closer to the singularity but not that close to it. Going earlier than that, I'm not sure how unique infrared's contributions would be. It's hard to look past that, except maybe with gravity waves or maybe neutrinos or something like that.

ZIERLER: When we're saying, "past that," do we mean prior to the cosmic wave background?

WERNER: Yeah, exactly right, because before that, the universe was largely opaque, and radiation from that earlier epoch tends not to get out.

ZIERLER: Just the chronology here, we're talking zero to 380,000 years.

WERNER: Something like that, yeah.

ZIERLER: That's the opacity that we're referring to.

WERNER: Yeah, although a point worth thinking about is that when people are talking about these things, they get very excited about the fact that they're looking back a zillion years. But what's really interesting is the time between what they're seeing and the Big Bang, because the further back you look, the less time there is for whatever it is that you're looking at to have gotten to the stage where you could see it. That's the JWST conundrum, if you like.

ZIERLER: Michael, a generational question, much more recent history, for you when you were in graduate school, was infrared astronomy already a mature discipline, or does your career sort of parallel the rise of infrared astronomy?

WERNER: See, I got my PhD in 1967—no, '68, I'm sorry. That's when the first, I mean, infrared had been done even before World War II, with relatively primitive instrumentation. But the 1960s is when the first modern infrared detector, which was called the bolometer, which is a device that measures the heat that falls on it. Its temperature changes, and you can sense the change in resistance as a way of detecting the radiation. That was invented in 1961, I think, by a man named Frank Low. During the subsequent years was when infrared astronomy really started to come into its own. I would say I was someplace between the first and second generation of infrared astronomers.

ZIERLER: It was definitely a hot topic. It was exciting to pursue in graduate school.

WERNER: Yeah, although in graduate school, I really worked on my thesis. I worked in the twilight zone between infrared and visible light at around 8 to 9,000 angstroms.

ZIERLER: We'll get to that.

WERNER: Yeah.

Career Duality at Caltech and JPL

ZIERLER: You have a unique perspective. You've served on the faculty here at Caltech in your long career at JPL. How do you compare the two environments, just from a research perspective? What kinds of research are more conducive to do as a professor? What kinds are more conducive to do as a JPL scientist?

WERNER: I think that distinction, particularly in astrophysics, is a fairly permeable barrier. I'm sure there's work that goes on at JPL with a component on campus, and vice versa. I left Caltech in 1979. I didn't get tenure. I don't really have a good up-to-date perspective. When I was there as an assistant professor, I really didn't have much independent agency, which is not the way things are done nowadays. But when you think about Caltech professors, you think about cutting-edge, knowledge-driven research with not necessarily large but significant research groups with graduate students, postdocs, and a professor in charge, and kind of entrepreneurial looking for funding sources, the NSF and foundations, and maybe cutting-edge facilities on the ground like LIGO, and the Keck Observatories and so forth. At JPL, the funding sources are somewhat constrained because we get all of our money from NASA, basically, or the DOD and three-letter agencies, which is a significant part of the JPL portfolio, as you probably know. But it's not easy to get funding from the NSF or even probably less so from a private foundation. Much of the research that goes on in astronomy and astrophysics at JPL, you could call it curiosity-driven, but it's often done either with data from a specific space mission or with a future space mission in mind or to test a promising new technology. I think that limits the scope of the research to things which are maybe a little more practical and focused than what might go on at campus., although There are always a few outliers. An important consideration is that at JPL, as you know, there's no tenure, and you don't have a guaranteed salary. Literally, you don't, I mean, legally, you don't have a guaranteed salary.

ZIERLER: Because it's all mission-dependent?

WERNER: It's not all—I mean, there's a fair amount of NASA-sponsored fundamental research. NASA runs a series of research programs, which are not specifically mission driven. They might be aimed at archival research from previous missions. They might be aimed at research which might be foundational for a future mission, or which might be demonstrating technology, which might eventually find its way into a mission. But they're basically all proposal-driven in some sense. For an individual scientist to raise enough money from research grants to support his entire salary is quite difficult. Most astronomers would be supported part-time by mission funds or by institutional discretionary funding and the like, and then partly supported by their own research grants.

ZIERLER: Michael, what about another generational type of question? JPL, it's right there in the title, the original mission was jet propulsion. JPL's early focus, of course, was planetary science. Do you see your career chronologically operating in parallel with JPL's getting involved in astrophysics?

WERNER: Yeah. I think there's an argument that can be made. I came to work at JPL in 1990 when what became the Spitzer project—it was then called SIRTF—was transferred from Ames to JPL. I brought with me a colleague named Peter Eisenhardt, who's gone on to be a very successful scientist at JPL, as a Project Scientist for the WISE mission, and so forth. Our arrival at JPL, without being too grandiose about it, is often seen as the start of the rebirth of JPL astrophysics.

ZIERLER: Rebirth?

WERNER: Yeah, probably the safest way to say it. After all, JPL played a major role in the Infrared Astronomical Satellite [IRAS] mission that flew in 1983. Soon after my arrival, a number of my generation of astrophysics leaders at JPL—Charles Lawrence, Bill Langer, Paul Goldsmith—joined the staff. In addition to Peter Eisenhardt, younger astronomers joined the party. One was Mike Ressler, whom I hired as a postdoc. He has done very well and is Project Scientist for the MIRI instrument on JW. Another early post-doc was Jamie Bock, now a professor at Caltech and the Principal Investigator of the SPHEREx mission. The whole field of astronomy and astrophysicists at JPL blossomed in part because, as Spitzer Project Scientist, I had a budget which allowed me to support a handful of scientists who then went on to be leaders in other scientific endeavors at JPL.

ZIERLER: Mentorship of younger scientists, even postdocs, that's been a big part of your work at JPL?

WERNER: Yeah. It's been almost a leitmotif or a day-to-day activity; not just the obligatory monthly meeting, if you understand the distinction. It's not something which was confined to specific points in time and space. It's something that goes on continually and to this day.

ZIERLER: How often at the busiest parts of your career would you find yourself at campus, or would you find needing professors to come up to JPL? I wonder if you can give a sense of that intellectual collaboration.

WERNER: Even starting when I was on the faculty at Caltech in the late '70s, my professional career has been the Spitzer Space Telescope. When Spitzer, in the development phase—let me just jump ahead. I had an office at the Spitzer Science Center [SSC] on campus, and I spent a few days a week there. Most of the science on Spitzer was done by scientists from the broad community who proposed to use the facility that we had built and launched for them and the SSC was the intermediary between the project and the science community

ZIERLER: Broad, you mean beyond PMA, beyond Tom Soifer, you mean, beyond Caltech?

WERNER: Yeah, exactly right. That Spitzer Science Center was located at IPAC on thr Caltech campus. Tom Soifer was the director of the Spitzer Science Center. There was a manager who handled more of the technical material, and so forth and so on. That was a very close coupling. I had an office at the Spitzer Science Center. I lived fairly close to the campus, so I might be over there one or two days a week. I primarily interacted with Tom and the other scientists at the Spitzer Science Center; not so much with the other Caltech faculty. I have done some work withTony Readhead, who's a radio astronomer here. He lives right across the street from me, and we became fast friends when my daughter Erica, who's a few years older than Tony and Carol's children, was their minder for a summer, leading to much hilarity and shared memories.

I've done some papers jointly with Tony, which involved radio astronomy and infrared data from Spitzer. Also, in a major research project on exoplanets which I led using Spitzer data I worked closely with Heather Knudson in GPS. There may have been other collaborations along the way. I did some work with Gerry Neugebauer before he retired; not so much based on Spitzer. But I think the relationship between the campus and JPL is a very intimate one and a very important one. We benefit from having visiting senior scientists from campus like Dimitri Mawet, Tom Prince, and others. Tony Readhead was one at one time. Of course, the campus and JPL benefit from being able to—and we benefit as well from being able to have access to the IPAC facility for mission support. The campus has access to JPL technology and facilities and expertise for mission development and operations. This is very clear from the current SPHEREx mission and from earlier joint activities such as Fiona Harrison's NuStar project. Conversely, JPL benefits from access to specific Caltech professors for technology assistance. There's a professor in EE whose named I think Kerry Vahala, or something like that.

ZIERLER: Vahala, yeah.

WERNER: He worked on what are called combs, laser combs, which produce a very precise frequency output, which has been incorporated into instrumentation at JPL, intended to study, to provide precise velocity data on stars which might harbor exoplanets, looking for the effect of a planet on the velocity of the star as they mutually go around the center of mass of the system. The planet goes around the star, but the star goes around the planet, in some sense.. Of course, we also benefit at JPL from the access to Palomar, which is basically a campus facility. At the same time, some of our JPL scientists have worked very effectively on instrumentation, which is being developed for Palomar. This is only in astronomy and astrophysics, where the coupling between JPL and campus is particularly tight. But of course, there is collaboration in planetary. Bethany Ehlmann is the PI on a lunar mission which is being largely done at JPL and IPAC, and so forth. The interpenetration is really extreme.

ZIERLER: A question about JPL—

WERNER: I should say, my access to campus was greatly assisted by my proximity to campus. Even before my wife died, even since my wife died—four years ago today, I might say—I've been one of the best customers at the Rath al Fresco.

ZIERLER: [laugh] Michael, a question about JPL directors. You've seen Ed Stone, Charles Elachi, Mike Watkins, now Laurie Leshin. How does that chain—

WERNER: Don't forget Lew Allen.

ZIERLER: Oh, you were under Lew Allen first, before Ed Stone?

WERNER: Yeah. Lew Allen was the director when what happened with the project was then called SIRTF is it grew beyond the obvious capabilities of the Ames Research Center—

ZIERLER: I see.

WERNER: —where it had been nurtured when it was a Shuttle-attached payload. When it became a free-flyer, it was basically put out to bid among the NASA centers, and JPL provided the winning bid, if you like. Then Charles Elachi called me and invited me to come down to visit JPL, because when the project came down, they wanted to hire me as Project Scientist, which I had been before. Lew Allen was the director at that point. I can remember when we came down here for an informational meeting, and he sort of put his arm around me, and took me out to the 9th floor of Building 180, and we looked out over whatever you look out of from there, and so forth. I was here for the tail end of his directorship, if you like.

ZIERLER: Even more so, the question is how the directors changed the overall feel and direction of JPL? How does that change from one director to another?

WERNER: I think it could have a tremendous influence, and I think it's most—Charles Elachi was a tremendous director, the best leader I've ever seen in my umpteen years of work at either Ames or JPL. But you see the difference. Mike Watkins, I think, was a little more reclusive, and Laurie Leshin has really opened things up with social events and her town halls, which are terrific, and her energy and enthusiasm. I think she's had, to my mind, a significant effect on the atmosphere at JPL, making it more exciting, more open. I'm not sure how much effect that's had on the man in the street at JPL. But to me, it looks like a big change.

From Chicago to Haverford

ZIERLER: [laugh] Let's go back. Let's establish some personal history now. Let's start with your parents. Where are they from? You grew up in Chicago.

WERNER: I grew up in Chicago, and my parents were both born in Chicago. Their parents were born—my mother's parents were from the Ukraine. I'm half Ukrainian, I'm proud to say. My father's parents were someplace called Galicia, which, depending on what day the week it is, is either part of Poland or part of Russia or maybe some other place in between. My grandparents all immigrated to the States in the late 1800s or the early 1900s.

ZIERLER: They went straight to Chicago?

WERNER: Boy, I'm a little uncertain about that. I think my mother's parents went straight to Chicago. My grandfather, my father's father, was all over the place but eventually ended up in Chicago…actually, he lived in Chicago when my dad was born, my grandparents, but then they moved to Knoxville, Tennessee, to be with my dad's sister, who was living in Knoxville. But my parents were both born in Chicago, and went to the Chicago Public Schools. My dad went to Northwestern University, studied accountancy, and ended up as a partner at Peat Marwick, which was one of the big seven or big five, whatever, accounting firms. My mother didn't get a college degree until much later, but went to nursing training, and worked as an office nurse in a doctor's office, and later as a music teacher in a private school in Chicago. She was very artistically inclined. After all the children left home—I have a brother and a sister—she went to the Circle Campus of the University of Illinois, the Chicago Campus, and got a degree in art—

ZIERLER: Oh, wow.

WERNER: —and was a very capable sculptress, dealing with large garden sculptures, and the like. My living room at home is sort of a gallery of her works.

ZIERLER: Oh, wow. Where did you grow up? What neighborhood?

WERNER: I was a tad—are you familiar with Chicago at all?

ZIERLER: Yeah.

WERNER: When I was a child, we lived in Rogers Park, near the Eugene Field School. When I was about 10, we moved to Evanston, and we lived in Northwest Evanston, which was largely a non-Jewish enclave at the time. We were among the first Jews to move into that part of the city.

ZIERLER: This was part of sort of an upward mobility migration?

WERNER: I wouldn't say that. I think it may have been to get us into better schools. I suppose there's some truth to what you're saying. The other part of it was that my parents were very involved with the Jewish community, and there was a young rabbi at the temple that they were going to, which was called Temple Mizpah. This was Rabbi Polish. He broke away, and started a congregation in Evanston called Beth Emet, and my parents were very much involved in the founding of that. By moving to Evanston, they got a little closer to it.

ZIERLER: This is a conservative shul?

WERNER: No, reform.

ZIERLER: Reform?

WERNER: Yeah.

ZIERLER: You went to Hebrew school on Sundays, that kind of thing?

WERNER: I went to Hebrew school in the afternoons, and got bar mitzvahed at Beth Emet.

ZIERLER: You went to public schools throughout growing up?

WERNER: Yeah. In Evanston at the time, the schools were excellent. I'm sure they're still very good.

ZIERLER: Were you always interested in astronomy and physics? Was that always your track?

WERNER: I was quite a good student as a child, and I was interested in math and science. I went off to college at Haverford College, which is a small liberal arts college near Philadelphia. When I got there, I wanted to be premed. Then, for some reason, I decided—I was a physics major from the start—I decided not to be premed. Here's the story, which is partly true.

ZIERLER: [laugh]

WERNER: At Haverford, like many other small liberal arts colleges in the Northeast, there was a little observatory, which had a classroom in it. When I was a junior, the astronomy professor at Haverford—there was only one—was teaching a course in that classroom. I would go to the classroom a couple of times a week, which was in the observatory, and there was a very charming little library there underneath a dome. There was a dome, a tower for the telescope, for a 12-inch telescope, something like that, and there was a library. Passing through the library, I saw a book on the table, which was called something like Frontiers in Astronomy or Problems in Astronomy, or something like that, by someone like Fred Hoyle or Isaac Asimov. I picked the book up, and I said—this is now an untrue detour.

ZIERLER: [laugh]

WERNER: I said, "Astronomy, I've always been interested in astronomy. If I had to do it again, I'd go into astronomy. But wait, I'm only 19."

ZIERLER: [laugh]

WERNER: But, anyhow, I took that book home and read it. I hadn't really thought about going into astronomy before then. That sort of would crystallize it for me.

ZIERLER: That's when you made the switch into astronomy?

WERNER: Yeah, basically. That's when I decided to go to graduate school in astronomy.

ZIERLER: Were there faculty at Haverford who were engaged in research?

WERNER: Yeah. In astronomy, there was a very fine old school gentleman named Louis Green, who I think had been a student of Henry Norris Russell's at Princeton, who was one of the first people to use digital computing in astronomical research. He did a lot of work on atomic structure and atomic energy levels and the like. He was the only astronomer there. In my senior year, he went on sabbatical to Princeton, but he came back every weekend. It's not that far. We would meet, and he would help me with my senior thesis. There were two other astronomers in my graduating class, one of whom was a guy named Joe Taylor, who got the Nobel Prize in physics for discovering the binary pulsar. During our senior year, since we didn't have any astronomer in house, we went over to Swarthmore every week to take a course in binary stars from a man named Peter van de Kamp, who was a legend in his own time, in many ways.

ZIERLER: What year did you graduate at Haverford?

WERNER: Oh, '63.

ZIERLER: Vietnam and the draft, these were too far out in the future? These were not concerns at that point?

WERNER: No, actually, I had a childhood illness, which got me out of the draft. I actually went and had a draft physical.

ZIERLER: Did you go to grad school right away?

WERNER: No, I didn't.

Cornell Astronomy

ZIERLER: You took some time off?

WERNER: I took a year off, partly because I didn't know anything about astronomy, and I got a job at a place called the US Naval Research Laboratory [NRL], which at the time was hiring. NRL had an astronomical research program, and they actually started out doing ultraviolet studies, launching instrumentation on captured German V-2 rockets. They were doing ultraviolet astronomy, and I got a year off to work there. I took a year off from school to work there, because I knew I wouldn't be drafted. I'd also met a girl from Bryn Mawr, who was much more sophisticated than I was in many ways and made me realize I had a pretty sheltered life. I tried to un-shelter myself for a year, not totally successfully. But I lived in Washington, D.C. I was there when Kennedy was assassinated. I worked in ultraviolet astronomy, went out to White Sands for a few rocket launches, and, most importantly, I met—well, after I decided not to go to graduate school, I had second thoughts, so I applied to some graduate schools in 1963, and deferred a mission—admission, rather, including from Caltech. But at Naval Research Laboratory, where I was working, there was a young astronomer from Cornell named Martin Harwit. He persuaded me to come to graduate school at Cornell.

ZIERLER: Aha.

WERNER: I did my graduate work under Martin's direction. You may be familiar with his, you must be familiar with his book, Cosmic Discovery.

ZIERLER: Of course, yeah, of course. Tell me about starting up the program at Cornell. Did you feel well prepared? Did you catch yourself up having not been an undergrad major?

WERNER: Yeah. It was no big deal because Cornell's astronomy program was pretty new, and was largely—what's going on here?—largely based as much on physics as on traditional astronomy. I didn't have any particular problem fitting in.

ZIERLER: How did you go—?

WERNER: I actually did my PhD in four years, which is pretty unprecedented in modern times.

ZIERLER: Yeah. Tell me about developing your thesis research.

WERNER: At the time, much of what we know now we didn't know. There was a problem, which may have been solved now by dark matter, but at the time there was uncertainty about—you can measure the mass in the galactic plane by watching the vertical motions of stars. They go up a ways, and then they're pulled back by the gravity of the matter in the galactic plane. That seemed to require more mass than the observable stars accounted for. A couple of Caltech professors, Tommy Gold and Ed Salpeter, had gotten very interested in what this missing matter was. You couldn't account for it by looking at the stars. There was some discussion it might be in the form of molecular hydrogen. My senior research was to look for molecular hydrogen in space, my PhD rather, which we did with an instrument that we borrowed from the University of Rochester, which was what's called a Fabry-Pérot interferometer. We set it up to look at wavelengths around 8,500 angstroms where there were a couple of molecular hydrogen emission lines, and looked at some regions of space where we thought we might see something. I think in the end, we had a very tentative detection, which was probably not even correct. But it was a good thesis project. I did some observing at Kitt Peak, and had a good time.

ZIERLER: Did Cornell have a relationship with Kitt Peak?

WERNER: Not particularly, but Kitt Peak is a public observatory. They had small telescopes there where you could bring your instrumentation, and bolt it on, which is what we did.

ZIERLER: What were some of the conclusions of your thesis?

WERNER: The main conclusion was that we didn't have conclusive evidence for molecular hydrogen.

ZIERLER: [laugh]

WERNER: In that part of the spectrum, there are also atomic hydrogen recombinant Paschen lines. We wrote a paper about the Paschen lines—or passion. I think it's called Paschen. That was the second conclusion. Then I did some theoretical work. It was known that when a molecular hydrogen molecule absorbed an ultraviolet photon, it would be excited from the ground state of the molecule into a higher excitation state. Some of the molecules in that excited state would dissociate. The energy would go into breaking the molecule up rather than into—well, actually, it would make a transition into the continuum level of the lower state.

The molecule would be dissociated as a result of having absorbed this ultraviolet photon. If it didn't do that, it would cascade down into some rotational-vibrational state of the original ground state. I'm sorry I'm making this very complicated. But you have the molecule in its ground state, some rotational-vibrational excitation, absorbs an ultraviolet photon, might dissociate, might cascade downward into a different rotational-vibrational state than it started in, and then cascade downward towards the ground rotational-vibrational state. I did some work on those processes, and actually wrote a paper about how molecules could be dissociated by this absorption process. You can imagine a dissociation wave propagating into a molecular cloud, say, and that general idea of it has become well-accepted. But an important thing about Cornell those were the days when you could get a postdoc if your thesis advisor knew somebody. My thesis advisor knew Fred Hoyle, because he, Martin Harwit, had been in England as a postdoc himself with Fred Hoyle. After one phone call, I had a—actually, what happened was I went to England on my honeymoon. At the time, they advertised academic positions in The London Times. There was an advertisement for an astronomer at Sussex, so I wrote to the guy at Sussex, and he said his position had been filled, but Fred Hoyle had a new institute at Cambridge that might be hiring. Martin Harwit knew Fred, and before I knew it, I had a postdoc position at Cambridge.

ZIERLER: Oh, wow.

WERNER: While I was there for a year, that was a great year, professionally. I connected with a man named Ed Salpeter, who was a great astrophysicist from Cornell. Although I hadn't worked with him at Cornell, I did work with him in Cambridge, and that led to some papers which were pretty important.

ZIERLER: He was on a sabbatical there?

WERNER: Yeah, exactly. I did some papers which were pretty important in the development of my career.

ZIERLER: What did you work on with him?

WERNER: I worked on one paper on the distribution of temperatures in an interstellar cloud, and was it cold enough that molecules, hydrogen molecules would freeze out on the surface of the grains in the inside? I wrote a paper about this and he had him take a look at it, and he was about to leave town, but he left me a message saying, "Don't submit this paper until we get a chance to talk about it." I'd made a very fundamental error in the paper in that it turns out that in a situation where radiation is percolating inwards into a cloud, the radiation is absorbed, and then it's re-radiated. The material at the center of the cloud is not totally shielded, and that re-radiation is enough to keep its temperature higher than you might otherwise think it would be. After we got that sorted out, and written up, we then started working with another one of his students, a guy named David Hollenbach, on the problem of under what circumstances would molecular hydrogen build up in a cloud, given the fact it would be dissociated by the radiation coming in from outside. We balanced the growth of the molecules on grain surfaces with the radiation coming in from outside, and predicted that there would be a lot of molecular hydrogen all over the place, which of course turned out to be the case. That was a paper by Hollenbach, me, and Ed Salpeter. Except for work I did on Spitzer, it's my most highly cited research paper. Of course, it was published in the early '80s—

ZIERLER: [laugh]

WERNER: —so it's had a long time to be popular.

ZIERLER: Of course, we have Fred Hoyle to thank for the term Big Bang, but he meant it derisively. By the time you connected with him, had he sort of gotten on the bandwagon that it really was the Big Bang, or he was holding out at that point?

WERNER: I didn't know him all that well. He was sort of this emperor-like figure who headed the institute. I think he probably held onto that, to that or other contrary ideas, until he died.

ZIERLER: Did you get to interact at all with him? Did you get a sense of who he was as a person?

WERNER: Not really.

ZIERLER: Just a sort of famous, removed individual?

WERNER: Yeah, exactly.

ZIERLER: It was a great experience for you, though, at Cambridge?

WERNER: Oh yeah, that was a great year. The institute was new, and there were great people there. George Field, who's a well-known astrophysicist from Harvard, was there, as was Ed Salpeter, as well as future superstars like Martin Rees and Joe Silk. This sort of traveling circus of Willie Fowler, and the Burbidges, and other dignitaries came for the summer. It was quite remarkable.

ZIERLER: You were on the job market that year as well?

WERNER: Yeah.

ZIERLER: You were applying?

WERNER: Exactly. Charlie Townes, who was a well-known physicist who invented the laser, and whose picture can be seen in the Hayman Lounge because he was a graduate student at Caltech, he started an astrophysics program at Berkeley. I wrote to him, and then he came over to Cambridge for a conference. I showed him some of the work I'd been doing on molecular hydrogen in interstellar clouds and the like, and he offered me a postdoctoral position, so I was a postdoc in Berkeley for three years before I joined the faculty at Caltech.

Berkeley in the late 1960s

ZIERLER: Was that a good move, looking back, to have an extended second postdoc in terms of your development?

WERNER: Yeah, I think so, because it allowed me to—definitely. I did some interesting research, and I got started in working in airborne astronomy on NASA planes, which later is what led me to be working on SIRTF.

ZIERLER: Ah. What were those first space-based missions for NASA that you were part of?

WERNER: The first one was a ground-based experiment, which at the time the cosmic microwave background had just been discovered.

ZIERLER: This is Penzias and Wilson?

WERNER: Yeah, and then people were trying to look at it from the ground, and so forth and so on. There was a lot of misunderstanding about whether there was spectral structure in the microwave background or not. I teamed up at Berkeley with a rather formidable crew consisting of John Mather, who went on to become the COBE and JWST Project Scientist. Paul Richards, who was a professor there, who was John's advisor, was an extremely good experimental physicist, turned to astrophysics, and we put together an experiment which we took to White Mountain in the Sierra to look for spectral structure in the background, which we didn't see. That was getting to work on an important problem with really good people. Then we started a program at Berkeley of observation with the NASA Learjet, which was the predecessor to the Kuiper Airborne Observatory, which flew for many years quite successfully, and evolved into SOFIA, which has had its ups and downs, and now it's down for good. But all of that success led me to a faculty position at Caltech. One of the main things I did at Caltech was a program of airborne astronomy on the Kuiper, which again had some great scientific results, and increased my visibility to the point that I was asked in 1977 to work on this project called SIRTF, where I led one of the community-based instrument teams, and got enmeshed into the process. By the time I was on the faculty at Caltech, when I didn't get tenure, it was natural to go to work at the Ames Research Center, which was (a) where the Kuiper Airborne Observatory lived and, (b), where the SIRTF studies were underway.

ZIERLER: Michael, what was it like being at Berkeley in the late '60s?

WERNER: It was pretty exciting.

ZIERLER: Yeah?

WERNER: Yeah. We were there when the university was shut down because of the Cambodian bombing, and participated in some protest marches in San Francisco, and there were a lot of flower child type activities. It was great. [laugh]

Joining the Caltech Faculty

ZIERLER: What was the point of connection at Caltech? Who would take notice of your work? Was it Neugebauer?

WERNER: Yeah, it was Gerry Neugebauer. I got invited down to give a talk by a man named Gary Steigman, who was a postdoc I'd met in Cambridge, who was a postdoc at Caltech. I was talking afterwards to Gerry and maybe to Eric Becklin, who was Gerry's right-hand man in a way. Gerry asked me point-blank if I was interested in coming to Caltech, and before long I had an assistant professorship offer. Part of the motivation was that Bob Leighton had just started to build his precision high frequency radio dishes, and it was thought that the best of these could be used for astronomical observations at a wavelength of 1 mm, far beyond the radio band. I started a program of mm-wavelength astronomy.

ZIERLER: Oh wow.

WERNER: Again, things were very informal in those days.

ZIERLER: Yeah. What was Neugebauer working on in those days?

WERNER: He was doing a lot of work at Mount Palomar, the 200-inch telescope. It was the kind of focus of the activity of the group. I started there in 1972. Now, a few years after that, Eric worked both at the 200-inch with Gerry and on the Kuiper Airborne Observatory with me. I learned much, much more from Eric than I did from Gerry. You might want to interview Eric Becklin to get an insider perspective on the early days of infrared astronomy at Caltech.

ZIERLER: He was just closer to it?

WERNER: He was much more accessible. Before too much longer, Gerry had gotten involved in the IRAS mission, where he eventually became the head of the US science team. That led to the foundation or forming of IPAC, which was formed to deal with the IRAS data. Again, returning to your theme of big data and so forth, I believe IRAS was the first publicly available, well-curated, and documented, machine-readable, and all that stuff, astronomical database. I'm not 100% sure about that, but it was certainly one of the first.

ZIERLER: How long did you stay involved with Kuiper when you joined the faculty?

WERNER: Oh, until Kuiper was decommissioned, which was after I went to JPL, I believe.

ZIERLER: Oh wow, a long time.

WERNER: Yeah.

ZIERLER: What were its science objectives?

WERNER: It was opening up the infrared spectrum because it was a 36-inch telescope. It flew up above most of the atmosphere, had access to regions of the spectrum which couldn't be seen from the ground, and everything we did was something new. It was very exciting.

ZIERLER: What were some of the new technological developments that made Kuiper such a leap forward?

WERNER: It was a little bit like Spitzer, in a sense. It provided, by virtue of the platform, it provided access to an unexplored part of the spectrum. You could take your detectors and instruments for a ground-based telescope basically, slap them onto Kuiper, and off you went. I don't sense that there was a lot of new technology, at least for the infrared part of the spectrum. Now, there was some high-frequency radio work that was done from Kuiper as well by Tom Phillips that may have required more technical development. Then as time went on, people were maybe flying small arrays of detectors and so forth, which was a new technology which really enabled Spitzer.

ZIERLER: Now, as Caltech faculty, did you have much interface with JPL?

WERNER: No.

IRAS and JPL Astrophysics

ZIERLER: Because this is before JPL was doing these kinds of projects?

WERNER: JPL eventually became the US center for the IRAS work.

ZIERLER: Right, but that was later?

WERNER: It was towards the end of my career on campus. When I didn't get tenure on campus, there was some interest in having me go to work at JPL. I went up to JPL to look around, and just sit in on a meeting of the IRAS science team and so forth. But I had a good opportunity at Ames, and I felt that if I stayed in Pasadena, I would always be under Neugebauer's thumb, literally or figuratively.

ZIERLER: [laugh]

WERNER: I broke away, reestablished myself, and came back as the Spitzer Project Scientist.

ZIERLER: How did you deal with the difficult news of not getting tenure? Was that a blow to you?

WERNER: It was a bit of a blow. It was a blow to my kids. But on balance, professionally, it was the best thing that ever happened to me.

ZIERLER: Oh, interesting. Because you took your career in new directions?

WERNER: Yeah, exactly right. In retrospect, I don't think I was Caltech faculty material. I could have stayed on as a faculty member, and had a successful research career, and who knows—

ZIERLER: You mean as a research professor?

WERNER: No, I mean, if I had gotten tenure, I could have stayed on, and had a modestly successful research career. But I probably wouldn't have achieved the uniqueness or the prominence that I achieved as a Spitzer Project Scientist. The way I like to say it is there are dozens of university researchers working at the level that I probably would have been working at, but only four Project Scientists for NASA Great Observatories.

ZIERLER: Yeah.

WERNER: It was a job that I was very well suited for.

ZIERLER: Did you ever get feedback on the decision where they felt you came up short, or those conversations really never happened?

WERNER: Not in any detail. I think Peter Goldreich was the chair of my thesis, my—

ZIERLER: Tenure committee?

WERNER: —tenure committee, and I think I went to talk to him about it. But I think we ended up talking about him somehow.

Ames and Kuiper Research

ZIERLER: [laugh] How did the opportunity at Ames come up? Did you already have connections there?

WERNER: Yeah, I had connections there by virtue of having worked on the Kuiper, and also by virtue of having been involved in the SIRTF studies, which were focused at Ames. I knew the people there pretty well.

ZIERLER: Tell me about the SIRTF studies. What was the project?

WERNER: We were putting together a—the committee I was involved with was called FIRST or something like that. Its job was to develop instrument concepts for SIRTF, which at the time was envisioned as a Shuttle-attached payload, which would fly several times per year, come back, change out the instruments, and all that.

ZIERLER: It was more modestly conceived in the beginning?

WERNER: Oh yeah, and there was an industrial study that was going on, an industrial study on the facility that was going on in parallel with our study of instruments. The whole idea was to put together a package that could be presented to NASA which would be irresistible.

ZIERLER: What made it irresistible?

WERNER: I think what would make it irresistible is the great gain in sensitivity from a cold telescope in space, and the idea that you could fly repeatedly with new instrumentation and all that, which was, of course, in retrospect, totally unrealistic.

ZIERLER: How come? Why was it unrealistic?

WERNER: The shuttle was not that flexible and versatile, and it was also a crappy place for a sensitive infrared telescope carrying its own cloud of molecular stuff, and it wasn't very stable. We had to worry about the heat of the Earth and all these things that you didn't have to worry- or worry about less about when you got into space.

ZIERLER: What happens next? How does the project grow?

WERNER: It grew to the point that in 1983, while it was still conceived as a Shuttle-attached payload—there's a book about this called Seeing the Unseen by a woman named Renee Rottner. Is that a book you're familiar with?

ZIERLER: No, but I'll have to get it.

WERNER: I have a spare copy in my office, and you're the most obvious recipient. What's your mail stop here, David?

ZIERLER: We'll figure that out. I'll get that to you.

WERNER: Okay, that's great. Anyhow, she details this early history. What happened was we put out in 1983 a call for proposals for the Shuttle-attached version of SIRTF. In the middle of that year, the results from IRAS came in and indicated that, yes, you could do a free-flying observatory in space. You could contain the liquid helium, the radiation environment, and not fry the detectors, and IRAS was absolutely a game-changer in terms of revealing the power of infrared astronomy. Midway through this procurement, a modification was issued in which you were invited to write a proposal which was both for a Shuttle-attached payload and for a free-flying payload. I'm not quite sure how you were supposed to—I can't quite remember how you were supposed to do this, but with bars on the side of the page, indicating that this part of the proposal applies only to the Shuttle, to the free-flying version, or something like that. I'd been designated the Project Scientist by then, but I had also joined one of the instrument teams, which was led by George Rieke. The original intent had been to do an over-selection, and then have competitions and technology development downstream. But the committee that oversaw the selection thought this was a bad idea, so three instruments were selected for development. At the same time, the decision was made to go away from the Shuttle onto a free-flyer. When the dust settled, SIRTF was a free-flyer with three instrument teams and a Science Working

Group [which I chaired], because in this procurement, you could also apply to be an Interdisciplinary Scientist or a facility scientist or whatever. This, of course, led to a special interest group which helped push SIRTF ahead.

ZIERLER: What was that group?

WERNER: It was the SIRTF science working group, which had been selected to take part in the flight, if and when the flight occurred. Another interesting footnote on history is that Frank Low, who invented the bolometer, and was a key member of the IRAS team proposed only for the free-flyer. I think that may be one of the things that swung NASA, because he was so influential, and particularly had a strong relationship with the scientists at Headquarters who were responsible for SIRTF. Thus his refusal even to be involved with the Shuttle-attached version, now that the free-flyer was known to work, may have helped swing the pendulum towards the free-flyer.

ZIERLER: The free-flyer program actually happened?

WERNER: It happened eventually. Bear in mind that this was 1984-ish, and we launched in 2003.

ZIERLER: [laugh]

WERNER: A few things happened in between.

ZIERLER: What else did you work on while you were at Ames?

WERNER: I had a very successful program of research on the Kuiper Airborne Observatory, and I did a lot of ground-based observing at the NASA Infrared Telescope Facility, which was just getting started, and also on the UKIRT, which is another infrared telescope in Hawaii. I was doing quite a lot of very productive research, a number of good papers, discoveries, dating back to that era in the 1980s.

ZIERLER: You were following the success of IRAS and the development of IPAC? That was relevant for you professionally?

WERNER: The success of IRAS was certainly relevant. I got funding to work on some of the IRAS data. I can still remember, in those days, there was a thing called preprints that were put out.

ZIERLER: Sure.

WERNER: All of the first IRAS results became a special issue in the ApJ Letters. But before that, they put out a big stack of preprints with glossy white covers and the IRAS logo, and I stayed up all night reading them. I could see that infrared astronomy had just taken a quantum leap forward. It was very exciting.

ZIERLER: Now, you were happy at Ames? You could have spent the rest of your career there, or when JPL came calling, that was a thrilling opportunity for you?

WERNER: Yeah. It's interesting that Ames is one of these places with a properly earned institutional inferiority complex. We always talked about those guys from JPL stealing our ideas and so forth and so on.

ZIERLER: [laugh]

WERNER: I'm not sure I was unhappy there. My kids were in school. My wife had a very good job at Stanford. By the time I got to JPL, my kids had graduated from high school. My wife still had a very good job at Stanford, which she had to leave when we came back to JPL. But I could see that for SIRTF, which is what I really wanted to do, JPL was a much, much better place.

JPL Appointment and Exoplanet Prehistory

ZIERLER: Who called from JPL? Who made that connection?

WERNER: Charles Elachi.

ZIERLER: Oh, it was Elachi?

WERNER: Yeah.

ZIERLER: What's the Elachi connection? What was he working on that was relative to SIRTF?

WERNER: He was the director of Earth and space sciences at JPL, and so he was recruiting. I didn't come to work with him. But I knew Tom Soifer quite well, and I managed that when I went to meet Charles, Tom was in the room. One thing led to another, and I was offered a job, and I was able to bring Peter Eisenhardt with me.

ZIERLER: It was the SIRTF program that you focused on when you went back to JPL?

WERNER: Exactly, yeah, so I have a kind of a skewed perspective of JPL because I entered at the top, basically, and I never was really in what's called the technical divisions, where most of the workers can be found, and where people are scrambling for support and all that. I was quite handsomely supported by SIRTF. Now, there was a time during the early days when big projects like SIRTF were in ill repute after the Hubble debacle.

ZIERLER: The resolution issue with the mirror?

WERNER: Yeah, and the failure of Mars Observer, and so forth and so on. One couldn't even say SIRTF. It was called the Infrared Astronomy mission. At that point, Charles intervened with some discretionary money, which we used to build a ground-based camera using one of the new detector arrays that were just becoming available. Mike Ressler had just finished work in Hawaii, and his wife was a doctor coming to Los Angeles, and so he fell into my lap as a postdoc, very capable, and he built this camera. We took it to Palomar, and then we took it to Keck, and made a great discovery while waiting for SIRTF to get restarted.

ZIERLER: Which was what? What was that discovery?

WERNER: It was a ring of dust around a star called HR 4796, which was clearly related to the presence or possible presence of a planetary system there. We got an actual image of it, which was so exciting.

ZIERLER: This was sort of the prehistory to discovering exoplanets?

WERNER: It was part of the prehistory. It wasn't in line with the discovery, per se. But one of the great discoveries from IRAS was something called the Vega phenomenon, which was infrared emission due to dust around normal main sequence stars. A lifetime of that dust is short compared to the lifetime of the star, which led to the indirect discovery of at least comets and asteroids around these stars, because something has to be replenishing the dust, which indicated that the first stages of solar system formation at least had occurred quite commonly around stars near the sun. That was in line with exoplanets, but it didn't really discover exoplanets. But the result on HR 4796 was exciting, because it was the first actual infrared image of this dust.

The Origins and Legacy of Spitzer

ZIERLER: How long was SIRTF active for?

WERNER: It became Spitzer after the launch in 2003, and it worked extremely well continuously till January of 2020.

ZIERLER: It was just a name change? Nothing really changed from the transition from SIRTF to Spitzer?

WERNER: Right. But all of the evolution of the concept and so forth had occurred while it was still called SIRTF. Originally it was the Shuttle Infrared Telescope Facility. Then it became the Space Infrared Telescope Facility, a free-flyer. In that guise, we got a very strong boost in 1990 from the Bahcall Committee, which was the astronomy and astrophysics review panel for the decade. When we were launched, we were SIRTF, but after we succeeded, we became Spitzer, named after Lyman Spitzer—

ZIERLER: Of course.

WERNER: —a famous astrophysicist at Princeton. His family didn't want to undergo the ridicule of Hubble bubble and all that sort of stuff that the Hubble family might have had to go through after the initial failure of Hubble.

ZIERLER: [laugh] A pleasant surprise from the Spitzer family, I'm sure, given how successful the Spitzer Telescope was.

WERNER: Yeah, exactly.

ZIERLER: What was launch day like in 2003? Were you on hand?

WERNER: Mm-hmm. The whole experience was jointly exciting and frustrating because we got delayed. First of all, we were going to launch in March, and our rocket was taken away from us to launch a Mars mission. These were all Delta II rockets. Then we were delayed further because it was part of the same business. We were launching into an orbit around the sun, so it had to escape the Earth's gravity. We had a bunch of strap-on solid rocket boosters to make that possible, and there was a problem identified with these boosters, which led to us being delayed further. Then we had a couple of additional delays because they were trying to put a boat out in the Indian Ocean to watch SIRTF fly by in case there was a debacle post launch. They wanted to make sure they had data on it. The boat eventually got there, but I don't think it ever got any data to speak of. When we launched, I sure was in the state of euphoria or disbelief. I chose to be in the control room rather than outside watching the launch, which was probably a big mistake. But it was very exciting, nevertheless. I can remember there were a lot of hangers-on from Ball Aerospace and Lockheed. They'd been our main contractors. They came to press the flesh of the NASA bigwigs, and to share in—and rightfully, because they were part of it—in the reflected the glory of the success, if it were successful, which it was. One of my strongest memories is of being at Kennedy Space Center in what's called the Rocket Garden, where they have erect duplicates or models, I mean, life-scale versions of all the rockets they've launched into space over the previous years, including some of the earliest NASA astrophysical exploration missions. I had this sort of epiphany of realizing that I was following in the footsteps of all these pioneers. It's a very powerful feeling.

ZIERLER: Yeah. When did Spitzer start to send back data? How long did you wait?

WERNER: We had to wait for the telescope to cool down. One of the innovations in Spitzer, a major innovation, was that we used passive cooling. We launched the telescope warm. Previous infrared missions IRAS and ISO had launched the telescope cold in a big, heavy cryostat, which more or less had to be shake-tested cold, and we finessed a lot of that. This warm launch was part of Frank Low's major contribution. It was facilitated by launching into an orbit where we didn't have to worry about the heat of the Earth; that was the heliocentric or sun-centered orbit [rather than the more usual Earth -centered orbit], which was brought to our attention by a JPL engineer named Johnny Kwok. We launched with the telescope warm, and the system was designed to lose a lot of heat just by radiation into space. Then we would start using our boil-off liquid helium gas to bring the telescope to an operating temperature. That took about six weeks overall. But after about three weeks, we could start observing with the IRAC instrument, which was least dependent on achieving lowest temperatures. That's when the data started coming back, and we knew we had a mission.

ZIERLER: Now, were you Project Scientist from the beginning, or you were named that later on?

WERNER: I was named Project Scientist when the science working—when the procurement went out for the—the announcement went out calling for proposals. I was named the Project Scientist. When I went to Ames, I wasn't the Project Scientist. There was a gentleman there named Fred Witteborn, who'd done a wonderful job—he's a Caltech graduate, in fact—a wonderful job of bringing the mission along to the point it had gotten at, dealing with all kinds of recalcitrant engineers and so forth and so on. I really respected him for that. But in the end, I became the Project Scientist. In the book that I'm going to send you by Renee Rottner, it's clear that Fred felt that he was treated unfairly, and I can understand why. But in the end I was a very good choice as a Project Scientist for SIRTF as it evolved into a free-flyer and so forth.

ZIERLER: Just because that was your area of expertise? It's what you were working on?

WERNER: No, it wasn't that. It was because a Project Scientist involves a lot of different—

ZIERLER: Skill sets?

WERNER: —skill sets, which I had or learned. Of course, I don't think Ames was up to the job, of managing the SIRTF development, and JPL certainly was.

ZIERLER: It was just too big of a mission?

WERNER: Exactly.

ZIERLER: Were you involved in the creation of this center at Caltech? Were you part of those considerations?

WERNER: The IPAC?

ZIERLER: Yeah.

WERNER: The Science Center?

ZIERLER: The Spitzer Science Center.

WERNER: Indirectly, yeah.

ZIERLER: What was the thinking? Why should it be on Caltech campus?

WERNER: It's logical. With the history of IRAS, IPAC was a logical site for the Spitzer Science Center, with the project being at JPL. I don't think any thought was ever given to having it be someplace else.

ZIERLER: What was the value of having the Science Center, I mean, what would have been missing if there was no center?

WERNER: If there was no center, there'd be no simple way for the community to take part in the mission, and anyone who did take part would have to learn the intricacies of reducing Spitzer data. We had 10,000 publications, 9,000 of which were written by people other than the original, or maybe 9,500 of which were written by people other than the original science team. Even then, the Science Center was invaluable in analyzing the data, and producing usable data products. You couldn't conceivably have a community-based observatory and a uniform archive and all that good stuff without a Science Center. They taught people how to use Spitzer. It helped develop the career of younger scientists. It had science conferences to publish the results. It assured that all data were reduced uniformly, guaranteeing a useful archive, which IPAC then established Being at Caltech, you had a lot of freedom, freedom of access, maybe freedom of action that wouldn't have been true at JPL necessarily. Now, what made it work particularly well is that Tom Soifer and I are very good friends. Under other circumstances, there has been, namely for SOFIA, tension between the Project Scientists and the Science Center. But Tom and I got along very well. Neither was interested in empire building. We were only interested in getting the right science done with as little politics as possible, and it all worked out very, very smoothly.

ZIERLER: Michael, let's review the achievements of Spitzer. What do we now understand about the universe that Spitzer made possible?

WERNER: I think the major, most lasting scientific result was the Spitzer work on exoplanets, studying the atmosphere of the exoplanets, discovery of the famous TRAPPIST system of seven exoplanets. The star formation history of the universe was largely written by Spitzer. Although it's now been perhaps called into question somewhat by JW, it's not clear how those results will play with the Spitzer results on the rate of the buildup of stars and stellar mass dating back to the early days of the universe. A lot of the properties of protostars, the efficiency of star formation, the characteristics of material that's going into young stars and and protoplanetary systems has been established by Spitzer. The commonalities, which are very important between our own solar system and exoplanetary systems, were dramatized by Spitzer. Spectra showing that the spectrum of comets, say, in our solar system is very similar to the spectrum of dust associated with exoplanetary systems, that's of course, I mean, you would think it'd have to be that way, but you don't know until you see it. That's very important in allowing us to draw parallels between our own solar system and exoplanetary systems. Numerous off-the-wall discoveries like a giant new ring about Saturn, you know, C60 molecules in interstellar space, the buckyballs in interstellar space were discovered by Spitzer. The spectacular spectrum of the dust from comet Tempel 2 that was the target of the Deep Impact mission was established by Spitzer, a very exciting result. Some of the fundamental properties of Kuiper belt objects, their masses in particular were determined by Spitzer because Spitzer could get the size of the Kuiper belt objects. The visible light just gives you the combination of the albedo and the radius, and Spitzer was able to determine the size of these objects, and some of them are quite large.

ZIERLER: Was it Spitzer that made IPAC a player in the so-called planetary defense world, looking at asteroids that are really far out, and their potential threat to planet Earth?

WERNER: Not so much. We did see some near-Earth asteroids, but Spitzer was not a good mission for surveying for asteroids. That was more done by WISE. Fundamental data on the properties of galaxies in the infrared, the list goes on and on. We had a series of what are called legacy programs with Spitzer, which were large programs carried out early in the mission to establish a legacy in case we had a premature end to the mission. Those were very productive scientifically in terms of studying protoplanetary systems, interstellar and circumstellar chemistry, star formation, and distant galaxies. The Magellanic Clouds have been well studied by Spitzer. The list goes sort of on and on. There's not a single area of astrophysics which was untouched by Spitzer. It is important to add that many of the most significant results from Spitzer were the work of teams selected from the community rather than work by the originally selected science teams. Spitzer's studies of exoplanets, as well as the Legacy Programs are good examples.

ZIERLER: That's incredible. How many missions can claim that breadth of discoveries?

WERNER: Exactly.

ZIERLER: It's really remarkable—

WERNER: Yeah.

ZIERLER: —and a pleasant surprise to some degree too, right? You had a good feeling it was going to be successful, but I imagine some of these aspects were just—

WERNER: Exactly. I couldn't imagine that Spitzer wouldn't work, but I had no conception of how powerful its results would be.

ZIERLER: Yeah.

WERNER: Of course, nature cooperated. Even for Spitzer to have seen the massive galaxies it saw back in early times, although maybe not as dramatic as JW, those results by themselves were surprising. Similarly, it is the prevalence of exoplanets [basically one or two or more around every star] which enabled Spitzer's exoplanet studies.

ZIERLER: Michael, are there any unsung heroes in Washington, either at the National Academies with the Decadal Reports or within NASA or on the Hill? Who are some of the people that might not have been scientists but were perhaps instrumental in making sure that Spitzer got off the ground?

WERNER: I would say the two most influential people in that regard, one was a woman named Nancy Boggess, who was the program scientist for Spitzer for infrared at NASA Headquarters during this time period, who was responsible for starting SIRTF for seeing—she was an astronomer, but mainly she was a scientific spokesperson, a very persistent and eloquent spokesperson for the infrared. She was responsible for overseeing that SIRTF, COBE, and SOFIA sere started. Then the other person I would mention was Charlie Pellerin, who was the head of NASA astrophysics in the '80s, and who, with Martin Harwit, developed the concept of the Great Observatories. The Great Observatories was seen as a family of observatories, including gamma ray, X-ray, visible, and infrared. The gamma ray member was the Compton Gamma Ray Observatory. The Great Observatories vision highlighted the importance of having complete multispectral coverage of the heavens. Once the Great Observatories program was established, then although Hubble sort of predated it, AXAF, as it was then called, now Chandra, and sort of now SIRTF/Spitzer came along naturally, because they were part of the Great Observatories program.

When we sold the Great Observatories program, the various members weren't such a hard sell as they might have been as individual, standalone science missions. Those, I would say, are the two people who are most prominent in the way you ask about. Now, Marcia Rieke, who became a member of the Spitzer Science Working Group, headed up a very effective sequence of visits to the Hill, and there were other staffers in Congress and so forth who certainly helped us along in addition. In fact, I knew we were doing well when we walked into the office of a guy named Doc Syers , who was staff on one of these congressional committees, and he said, "Hello, Marcia." She was well enough known to be on a first-name basis with the key decision-makers in Congress. Another NASA scientist to whom I should give a shoutout is Ed Weiler. He was either the head of NASA Astrophysics or the head of NASA science during the key moments of the SIRTF development, who is of course well-remembered for advocacy of the Hubble Space Telescope as well. Ed was kind of gruff in public meetings, but in some private discussion I had with him about whether I should be the Project Scientist or apply for the position of Head of the Spitzer Science Center he was very empathic and helpful. He of course recommended that I stay as Project Scientist, which was the right choice.

ZIERLER: Michael, what about the lifespan of Spitzer? Did that more or less accord with what the plan was? Did it go for longer than was expected?

WERNER: Much longer because of the fact that since we're using radiative cooling, we recognized that once we ran out of helium, which happened about six years into the mission, longer than predicted, the telescope would stay cold enough that we could keep on operating with our two shortest wavelength detectors, which we did. That was the so-called Warm mission, which was particularly influential in the study of exoplanets and in the exploration of the distant Universe, which carried on for the next 14 years, just using the two spectral bands. We realized once we adopted the Warm launch, and the radiative cooling, and the drift away orbit, solar orbit, that we could probably go on in this mode or mission mode more or less indefinitely, but it was much more that nature cooperated, and it was much more successful than anybody anticipated.

ZIERLER: Were you tracking the early discussions that ultimately would become JWST? Were you following that?

WERNER: I was an early part of their advisory apparatus.

ZIERLER: How big did Spitzer loom in those early discussions about the next generation of infrared?

WERNER: Very large, because of the scientific results, and because of the demonstration of radiative cooling, which was critical for JW.

ZIERLER: It's fair to say that Spitzer being a smash success was instrumental to JW becoming a reality?

WERNER: I think so. I would say so, and everybody might not agree with that, but that's my take on it.

JWST and a New Dawn of Astrophysics

ZIERLER: Were there limitations to Spitzer, because there are always limitations with current technology, that specifically went into what kinds of capabilities would be envisioned for JW?

WERNER: In my judgment, there were. They have to do with the resolving power and the wavelength coverage of the Spitzer spectrographs. Even though Spitzer had photom…well, first of all, of course, Spitzer only worked down to 3.5 microns, and there's a big part of the spectrum shortward of that which is very important if you're studying stars and galaxies and things. But, in addition, our spectral coverage of our spectrograph only started at 5 microns, and our highest resolving power was only 600, which was available only longward of 10 microns. The JW spectrographs have much better wavelength coverage and much higher spectral resolution. The other thing that we didn't have on Spitzer because, well, we were constrained by programmatic and financial considerations to keep Spitzer as simple as possible, so it had no moving parts basically except a scan mirror in one of the instruments, which was essential to make it work. But we didn't have a lot of bells and whistles and things. With JW, they were able to provide coronagraphic instrumentation, which can go part way to blocking out the light from the star, and making exoplanets more visible, and that we didn't have on Spitzer; we couldn't have had, because we didn't know we needed it at the time.

ZIERLER: I asked about land-based—

WERNER: Also, I should say, our biggest detector array on Spitzer was 256 by 256, and JW has got 2K by 2K arrays.

ZIERLER: This is pixels you're referring to?

WERNER: Yeah, exactly.

ZIERLER: Yeah, much higher res?

WERNER: Yeah, much more, yeah, exactly, and of course 50x the collecting area of the primary mirror.

ZIERLER: Michael, I asked earlier about land-based astronomy. The success of Spitzer, did that influence land-based new telescope missions?

WERNER: Getting back to JW for a second, in the original concept, JW didn't have any infrared capabil…and it didn't have the MIRI instrument, which provides its longer wavelength capabilities. I'm sure the success of Spitzer was one of the many considerations that led to the inclusion of MIRI in the final payload. I think that's right. Land-based telescopes? I'm not so sure, although it certainly provided impetus to the idea of having infrared capabilities on these upcoming 30-m class telescopes. The one small possible example is the TRAPPIST mission. TRAPPIST was a Belgian-led ground-based mission to look at M stars for exoplanets, M stars being later-type stars where, if you found planets, they would transit more frequently, they'd be closer to them, and so forth, and the star being fainter would make it easier to see the planet, perhaps.

TRAPPIST-1 was the first planetary system discovered by the TRAPPIST project, and they were seeing transits, but there was a lot of ambiguity because they could only observe it 8 or 12 hours a day, and miss days because of the weather, what have you. They applied for and got 20 consecutive days of time from Spitzer, which allowed the disambiguation of this planetary system, and maybe helped to lead to a more sophisticated project called SPECULOOS, again, a Belgian delicacy with a very torturous acronym to spell it out. But I think that there hasn't been a TRAPPIST-2 or a SPECULOOS-that I'm aware of, though TRAPPIST-1 was a great discovery which got Spitzer at least another year of life. So far, it seems to have been a bit of a flash in the pan, but it helped us a lot, and it's been very exciting. Three or four of the seven TRAPPIST-1 planets are Earth-sized planets close enough to their star to have Earth-like temperatures.

ZIERLER: The so-called habitability zone?

WERNER: Yeah, exactly, and they're prime targets for JW. There's a wonderful JW paper on one of these planets which shows no evidence for an atmosphere, and you might get discouraged. But then you have to remember that they were measuring thermal emission from a planet the size of the Earth, not too much warmer from the Earth, 40 light years away. That's not too shabby.

ZIERLER: [laugh] When the Spitzer mission finally concluded, what did that mean for you? How did your day-to-day change?

WERNER: It eventually led to my—I think I was probably half-time. I can't remember when I went half-time at JPL, but it might have been around the time that the Spitzer mission ended.

ZIERLER: You looked at your eventual retirement along a similar timeline to the Spitzer mission?

WERNER: Something like that. Then as the Spitzer support waned, which it did with time, of course I became a Co-I on SPHEREx, which provided some support. Then I approached my colleague Charles Lawrence, who'd taken over from me as the Chief Scientist for physics and astronomy, and suggested to him that I would work on our Palomar investment, and he'd provide the funding to help keep me going, between the two sources of funding, I am supported for 10 or 15 hours a week.

ZIERLER: That's basically where you are now?

WERNER: Exactly, yeah.

ZIERLER: Michael, now that we've worked right up to the present for the last part of our talk, if I can ask some retrospective questions about your career, and then we'll end looking to the future. Broadly conceived, what have been the most exciting things in your career, what we now understand, thanks to infrared astronomy, what really stands out in your memory?

WERNER: There are two parts of my career that I'm particularly thankful for. I've been very, very fortunate. I've worked with very good people and had outstanding mentors I've had good opportunities. Of course, successful scientists are opportunistic. I think we have a much better understanding of the processes of the formation of stars and planetary systems and even exoplanets than we did when I started or even well into the—IRAS sort of blew the field open, to some extent, but Spitzer provided great amounts of detail about these fundamental processes that control both the evolution of galaxies and the formation of life. All that is really grist for the mill of infrared astronomers. In addition to that, of course, we had a much better picture based on Spitzer, which is now being embellished or developed by JW, of the way that galaxies have formed and evolved over cosmic time. It's well to remember that there's a certain sense of wonder about all this stuff, a lot of the things. It's amazing that we can do the things that we do, but a lot of the results are really amazing, I mean, sort of like the TRAPPIST-1 system, who would have dreamt of that? Anything that can happen will happen!

ZIERLER: Yeah.

WERNER: The rich infrared spectrum of the debris of comet Tempel 2, the one that was crashed into by the Deep Impact mission, no one anticipated how fruitful that result was going to be. We have a Spitzer result which shows the conversion of interstellar silicates of circumstellar silicates from the amorphous variety, which is common in interstellar space, to the crystalline variety, which is common in the exoplanetary system and in our own solar system. These marvels are just one on top of the other, and many are things which couldn't have been anticipated. You really have to step back and say, "Wow, isn't nature wonderful?" That's kind of one aspect. Also, we've nurtured a lot of young scientists personally. Many people did their PhDs on Spitzer data, and have gone on to successful careers in astronomy or maybe not in astronomy. That's OK too. We've had a good—particularly through TRAPPIST-1 but through other work—we've had a good footprint in the public community. We've been on the cover of textbooks. We've rewritten textbooks. Just a rich and very rewarding scientific bounty which, as you said earlier, I could never really have conceived of.

ZIERLER: That's right.

WERNER: The other thing is that it's been very gratifying to me personally to play a leadership role in this whole process, going back to square one, or going back to Ames and then to the development of SIRTFas it became Spitzer here at JPL. If I hadn't worked on Spitzer, it probably would have happened, but it might have been a rather different mission and a different development process. Who knows? But one of the things I've learned is that you can have all the processes and procedures and rules and guidelines that you want. The success of the project ultimately depends on the people who work on it.

ZIERLER: Absolutely.

WERNER: I've learned that there's no force more powerful than human intuition, energy, and drive, persistence, all those positive attributes, when you have a group of people who have a common purpose, and who are well motivated and empowered to use their abilities to achieve that purpose and to work together. One of the things I remember about Charlie Townes is that we had a banquet in his memory or his honor, rather, I'm sorry. I think it was at the San Diego Zoo, of all places.

ZIERLER: [laugh]

WERNER: He said that science is a constructive human endeavor, which is not a zero-sum game. A project like SIRTF, everybody who worked on it, is a winner. There were some people who lost out when their proposals weren't accepted, but that was a long time ago. I think a project like SIRTF, I've said this repeatedly, is an example of the very best that human beings are capable of. You could say the same about JW, and other NASA missions, and other things in other walks of life. But it's wonderful to see something that's so complex, so demanding, and so successful in an era when it's easy to be negative about where we are and where we're going.

ZIERLER: That's right.

WERNER: I'm very proud of having been one of the people, perhaps the most influential single person in having made this happen.

ZIERLER: Michael, your unique experience of the negative experience of not having achieved tenure, and then going on to accomplish what you did, what are the life lessons there? How did you not become embittered and sort of closed off from the field? What's to learn from your experience, your response?

WERNER: One thing you could learn, of course, is that what seems bad at the time may not be bad in the long run. I've never really lamented the fact that I didn't get tenure by looking back and said, "If only I'd done this. If only I'd done that." I think probably way down deep, I knew it was the right decision for me, or could be made to be the right decision for me. I was able to apply my skills and my temperament and my personality in a way that made best use of all of them. I guess that the lesson is to look for opportunities if you can, not to regret the past so much as to use what you've learned in the experience, and look at opportunities where you can put your capabilities to the best use. I was also very fortunate to have had excellent mentors and guidance along the way. I mentioned a number of these people. Martin Harwit, Paul Richards, Charlie Townes, Eric Becklin, all had tremendous influences my career, and I've had equal influences on the careers of the next generation of scientists.

ZIERLER: Michael, of all of the awards and honors you've received in your career within NASA scientific societies, what's been most personally meaningful for you in the way you've been recognized?

WERNER: I would say, one, I was chosen by the Royal Astronomical Society as what's called the George Darwin Lecturer in 2006. That's a very public, relatively public view, recognition rather, that will go down in history. There'll be a list of recipients of the Charles Darwin Lectureship, and there I'll be in 2006, between astronomer X and astronomer Y. I think probably the other thing would be being named a JPL Fellow. I was only the second scientist ever to be chosen for that award. There's something about the recognition of your peers or your close associates which is really important, and can't be—

ZIERLER: It's kind of the ultimate corrective to not getting tenure at Caltech.

WERNER: Exactly, yeah.

ZIERLER: [laugh]

WERNER: Another thing, which I hadn't mentioned, which was very rewarding to me was that I wrote a book based on the results from Spitzer. It's called More Things in the Heavens, published by Princeton University Press. I wrote it with my co-author Peter Eisenhardt, who had come with me from Ames to JPL. Princeton University Press is a very prestigious press, and they did a beautiful job with this book, of which I hope you have a copy.

ZIERLER: I don't, but I'll get one.

WERNER: It summarizes the rationale for infrared astronomy and the results for Spitzer in a way, which I think is quite satisfying, and has sold more than a dozen copies.

ZIERLER: [laugh] Finally, Michael, let's look to the future. Using your powers of extrapolation, you witnessed the earliest conversations of JW. You see where Spitzer fit in. What's next? What comes after JW?

WERNER: I would say that programmatically within the NASA family of observatories, the next big observatory, really big observatory is one called the Habitable Worlds Observatory, which is aimed at actually studying the habitability of Earth-like planets around nearby stars. That's a tall order for a number of reasons, to be very challenging technologically, and may not happen for another—I'm 80 years old now. I'll be delighted to be alive when it's launched. People are very clever, and they may find ways of studying this habitability issue with existing instrumentation more capably than people envision at present, although it's very difficult to do. I think.With LIGO with gravitational radiation, and possibly neutrino astronomy, and other examples as well, we're on the verge of major new fields of research being created and embellished, which is very exciting. But, on the other hand, I think if we don't get to work on global warming, it's all going to all be for naught, unfortunately. I was fortunate to be well-compensated in my years at JPL, and my wife made a good salary working at Stanford and USC, and we have TIAA-CREF and all this good stuff, so I was able to endow both at Caltech through the SURF program and at Haverford fellowships. Some are stipends for people who have internships and aren't getting paid so they could afford to take the internships. I have specified that the selected students should work in the area of climate science.

ZIERLER: Oh, that's wonderful.

WERNER: —which in practice means working in areas related to climate change; a small, little contribution.

ZIERLER: After a career in fundamental research, something applied?

WERNER: I think it's—as much as I hate to say it—it's much more important than astronomy.

ZIERLER: There's no doubt. Finally, for you, looking to the future, for however long you want to remain active—I'll limit it to SPHEREx, since that's your current project—what do you want to accomplish?

WERNER: I'd like to help see that SPHEREx is successful, and to be a co-author of a couple of papers coming out of the Ices project that I work on. I enjoy very much the—I realized the other day, I can't quite remember the details, that I had two or three conversations with different scientists about different aspects of SPHEREx and maybe Palomar. I'd like to remain relevant long enough to continue such conversations for at least another four or five years.

ZIERLER: Because it's still fun? It's still interesting?

WERNER: Yeah. I've really enjoyed talking with you, although I'm doing most of the talking. There's nothing quite as exciting as being in a stimulating one-on-one conversation with a colleague where you're maybe—I decided I wanted to do a poster. There's a conference on astronomical surveys coming up here at Caltech at IPAC in October. I decided we should submit a poster on SPHEREx's work on the diffuse interstellar medium, which is not our main line of work but one where SPHEREx, being an all-sky survey, will create a fantastic archive in the spirit of IRAS and WISE and so forth. This is a topic where we can stimulate really exciting work, and there's a new scientist at JPL who is very interested in it, which is fun kicking around with him what we should put into this poster. Then the same day, I had another couple of conversations with other folks about scientific topics, and it was really, really a good way to spend the day, and I'd like to be able to do that to some extent for the next few years at least.

ZIERLER: Michael, it's been a wonderful conversation. I want to thank you so much for doing this.

WERNER: You're very kind, David.

[END]